Breather tubes drip oil

[tanman496]

I have a 8V71 and there are a couple what looks like to be like a a 1/4 inch breather tubes that hang down and they drip oil what causes this and what would it take to fix it I live in upstate NY and they wont pass the nys inspection if it has signs of oil leaks. I am getting so frustrated

[lostagain]

Mark, those drip tubes, or slobber tubes, normally drip an oil and moisture residue out of the air boxes in 2 stroke Detroits. Some have check valves that close at higher pressures like anything above idle, so they only discharge at idle. Many of us install catch cans under them so it doesn't make a mess on the ground and on the back end of the bus. I use 12 or 16 oz energy drink bottles. They have a wider neck and stronger plastic. I drill a hole in the cap and push it up the tube. Then I put on a small hose clamp on the tube just under the cap, so it doesn't slide down, and screw the bottle to the cap. I also drill a small hole near the top of the bottle for air to escape as the oil is being blown into the bottom. Just drain them once in a while. That should satisfy the emissions inspector.

JC

[luvrbus]

On the incline engine in your bus both drains should be on the left side easy to get reach to clean the check valves

good luck   

[Geoff]

The correct name for them are air box drains, and you shouldn't have any oil or barely any oil coming out of them unless there is a problem with the engine.  Blower seals are a possibility, but it could also be a problem with the piston oil control rings.  It seems a lot of people just accept oil leaking through the tubes and that is why they put catch jugs or collection tanks with a drain.

[kingfa39]

my mechanic put a check valve on mine and routed it back to the block, that was 32 yrs ago and never ever had a problem, still there still working, the mech was a ex greyhound mechanic retired now deceased but knew what he was doing.
Frank allen

[Van]

Lol, I was just thinking about that Frank. What about it fella's, the advantage of routing them into say the pan or where ever is obvious, what about the Con's?

[luvrbus]

They did that for the state of CA with transit and bus engines turned out not to be a great idea they issued a service bulletin against the idea funny thing you can still buy the parts for setup from a DD 

Bobofthenorth has the setup on his 8v92 without it going back into the pan he probably could have seen the problem and saved a engine and some big bucks

good luck

[Geoff]

Lol, I was just thinking about that Frank. What about it fella's, the advantage of routing them into say the pan or where ever is obvious, what about the Con's?

The cons are you have a problem with your engine that you are avoiding fixing and the reason I got from Detroit Diesel not to route the drains back into the oil pan was that the air box contaminated the oil which resulted in crankshaft failure. 

Putting a jug or cannister to collect the oil is a Band-Aid, routing the lost oil back into your oil pan can lead to disaster.

--Geoff

[Van]

It is obvious there are problems if you are blowing oil out of the puke tubes (as I refer to them ), Thanks for bringing up contamination, this was my only concern Geoff.

[kingfa39]

The air box drains only have a very small amout of oil coming out, this is a argument that has been going on ever since i put them on my 06, 25 or 30 yrs ago, never a problem. and i had a GM notice somewhere that promoted it but cant find it now, can also be run into a container on the side somewhere if you are worried about it, but like i said i wouldnt do anything different. if the oild is changed as suppose to be should be fine
Frank Allen

[robertglines1]

First things first, Make sure the air box drains/check valves work. They can be cleaned and restored to working order in most cases. They should close around 900 rpm keeping all pressure in air box/engine and nothing coming out drains and dripping on road -back of bus or toad. Or put catch cans on them.  If they work correct the discharge above 900 rpm will be burned thru the engine: you will never notice it.  If you do you have a problem.  It worked for me.  I replaced mine on the 8V92 for $42 each and kept toad clean without catch cans . On a 8V71 I had I just cleaned them--make sure you put the check valve back the correct way.   Bob

[luvrbus]

Frank you must have a slant GM bus that the only engines they were used on and they don't come from the block the paper work I have show those replaced a couple of the air box covers fwiw they don't drain very good either, there is a bulletin from DD telling dealers to remove those when I find time I'll post the number for you 

Any 71 or 92 series manual will show those on slant engines

good luck

[tanman496]

Is my 1980 gmc with 8V71 Suppose to have the check valve and can you tell me what it looks like all i see is tubes hanging from the side of the block

[robertglines1]

if they were still there . would be about size of a shotgun shell and screwed into block with hose attached to it.  Air Box drain.  Not uncommon for them to have been removed rather than replaced. They did that more common on construction equipment than road vehicles(buses & trucks)

[luvrbus]

I wouldn't worry to much about the check valves some engines had the valves some didn't it all depended on the oil ring group specs for the expansion ring behind the oil ring it's self 

Don't let the engine idle for long periods and they don't drip unless there is a problem live with it or make a catch can


good luck